JP2008171983A - Light source device, image display device, projector and light source control method - Google Patents

Abstract

In a brightness variation adjusting means for individually adjusting brightness variations of a plurality of light sources connected in series to a constant current source, power use efficiency is improved and power saving is supported.
A plurality of light sources 1 to 4 connected in series and light sources 1 to 4 are lighted at a maximum brightness by continuously turning on a reference light source 1 that has been observed to have the lowest brightness due to brightness variations among the light sources 1 to 4 lit at a constant current. A constant current source 5 for supplying a reference current to both ends of the series connection, and control elements FET1 to FET1 connected in parallel to each of the plurality of light sources 1 to 4 and bypassing the applied voltage of each of the light sources 1 to 4 by PWM control. PWM in which the PWM signal for each light source 1 to 4 for controlling the OFF period of each of the light sources 1 to 4 based on the brightness suppression data for each light source by the bypass ON of each of the control elements FET 1 to FET 4 is individually output. And a control circuit 6.
[Selection] Figure 1

Description

  The present invention relates to a light source device, an image display device, a projector, and a light source control method.

  In recent years, as the demand for miniaturization of projectors has been increasing, light source devices, image display devices, and projectors using these LEDs as light sources have been studied as the output of light emitting diodes (LEDs) increases. LEDs have great potential as next-generation display elements because they can be reduced in size as well as reduced in size and flattened.

  By the way, in order to individually adjust the variation of each LED element, a matrix type drive is required. Further, a high power driving LSI or the like required for a driving device for an LED with high power consumption has not yet been developed for each light source application such as a backlight of a display device or a powerful light source for a projector. At present, a series connection type that can be compromised in terms of cost is used, but with this series connection type, it is difficult to adjust the luminance variation of individual LEDs.

  Therefore, when a plurality of light emitting elements connected in series, for example, LEDs are driven at a constant current, a constant current source that can individually adjust the luminance variation of each LED element is driven by the constant current source. A backlight light source device and a color liquid crystal display device are known (see, for example, Patent Document 1).

Specifically, it is a constant current driving device that drives a plurality of LEDs connected in series by a constant current driving circuit using a pulse width modulation constant current driving circuit, and a load resistor is connected in parallel to each of the plurality of LEDs connected in series. A transistor connected to the base and emitter of the transistor, and a capacitor connected to the base of the transistor, and a switching control signal is supplied to the base of the transistor via the capacitor A control circuit for controlling the switching of the transistor by the control circuit, so that a drive current flowing through the plurality of elements connected in series is shunted to the load resistor.
Japanese Patent Laying-Open No. 2005-310996 (paragraph 0011, FIG. 11)

  However, the pulse width modulation constant current driving circuit disclosed in Patent Document 1 is not necessarily good in terms of power utilization efficiency, and is a luminance variation adjusting unit that individually adjusts luminance variations of a plurality of light sources connected in series. Therefore, further power saving measures have been desired. The present invention has been made in view of the above problems, and its object is to eliminate unevenness in the amount of light while the light source has a luminance variation within a single element or between adjacent elements due to low quality. An object of the present invention is to provide a light source device, an image display device, and a projector that are capable of reducing power consumption.

In order to achieve the above object, the present invention provides the following means.
The light source device of the present invention includes a plurality of light sources connected in series, and a reference current that emits light at a maximum luminance by continuously lighting a reference light source that has been observed to have the lowest luminance due to luminance variation among the light sources that are lighted at a constant current. A constant current source that is supplied to both ends of the series connection, a control element that is connected in parallel to each of the plurality of light sources, and that bypasses the applied voltage of each of the light sources by PWM control, and each of the control elements that is bypassed ON And a PWM control circuit for individually outputting a PWM signal for each light source that controls an OFF period of the light source based on luminance suppression data for each light source.

  According to the light source device of the present invention, the luminance variation is observed in advance to identify the reference light source having the lowest luminance, and the data regarding the luminance variation for each light source is stored so as to be usable as the luminance suppression data for each light source. A constant current that emits light with the maximum luminance by continuously lighting the reference light source is determined as a reference current and supplied from the constant current source. If this reference current is maintained, light sources other than the reference light source are lit brighter than the reference light source in accordance with the luminance variation, so that it is necessary to suppress the luminance for each light source.

  Therefore, the PWM signal for each light source controlled based on the luminance suppression data for each light source is individually output from the PWM control circuit. When the PWM control circuit controls the OFF period of each light source by the bypass ON of each control element based on the brightness suppression data for each light source, the brightness is increased by a short OFF period and the brightness is decreased by a long OFF period. There is an effect.

  By this action, constant current control is performed so that the maximum luminance of the darkest light source is continuously emitted with the reference light source as the reference light source. Then, by limiting and suppressing the light sources other than the reference light source exceeding the reference light source and being too bright, it is possible to individually adjust the luminance variation. With respect to the light source during the OFF period in which the luminance is suppressed, the power efficiency is improved only by the fact that the power consumption is almost eliminated.

  In such a light source device that drives a constant current by connecting a plurality of light sources including luminance variations with respect to current values in series, the power consumption is improved by controlling the OFF period based on the luminance suppression data for each light source. It is possible to individually adjust the variation.

  In the light source device of the present invention, it is preferable to use an LED for the light source. In particular, a high-power LED has high luminance and good power efficiency, so that the light source device can be reduced in size and weight and further reduced in power consumption.

  Further, the luminance suppression data for each light source in the light source device of the present invention is configured so as to exclusively control an OFF period of each of the plurality of light sources connected in series by being input to the PWM control circuit. It is preferable. The OFF period of each light source in such a light source device is an ON period of a control element that bypasses each light source.

  A plurality of light sources are connected in series to the current source, and control elements connected in parallel for each light source are also connected in series to the current source. Here, if the OFF period of each light source is not exclusive, there is a risk that a plurality of control elements connected in series will all be turned on simultaneously without resistance and short-circuit the current source. Can avoid the dangers. In addition, since only one of the plurality of light sources is turned off exclusively, the power fluctuation can be reduced and stabilized.

  Further, the light source device of the present invention includes a luminance sensor that detects luminance data for each light source arranged in the vicinity of each of the plurality of light sources in real time, and luminance suppression for each light source based on the luminance data from the luminance sensor. And a luminance sensor control circuit for generating data and inputting the data to the PWM control circuit.

  According to the light source device of the present invention, since the luminance sensor detects the luminance data of each of the plurality of light sources in real time, it is possible to save the trouble of creating the luminance suppression data for each light source, for example, when the product is shipped from the factory. Also, if there is a malfunctioning and unlit light source among a plurality of light sources, a certain level of brightness can be maintained by a normal light source by bypassing the light source.

  Moreover, the image display apparatus comprised including the light source device of this invention can be provided. Furthermore, a projector configured with the image display device can also be provided. Also in these image display devices or projectors, it is possible to obtain the same effect as that obtained by the light source device of the present invention.

  In the light source device control method of the present invention, the darkest light source specifying step of observing the luminance variation of each of the plurality of light sources and specifying the reference light source having the lowest luminance from the light sources, and continuously turning on the reference light source The reference current supply step of supplying a constant current to be emitted from the constant current source by setting the constant current to be emitted at the maximum brightness as the reference current, and the luminance suppression data for each light source that generates the luminance variation data for each light source as the luminance suppression data for each light source Each light source OFF period in which the OFF period of each light source is controlled by inputting the PWM control signal for each light source to the gate of each control element based on the luminance suppression data for each light source and bypassing each light source based on the generation step And a control step.

  Hereinafter, embodiments of a light source device, a projector, and a monitor device according to the present invention will be described with appropriate interweaving of the configuration and operation of each unit with reference to the drawings. In each figure, the same function is denoted by the same reference numeral, and description thereof is omitted. In addition, although the light source is appropriately read as LED, in the drawings, all light sources are collectively described.

  FIG. 1 is an explanatory diagram of a light source device E according to the present embodiment. FIG. 1A is a schematic circuit diagram, and FIG. 1B is a correction magnification and luminance suppression data for a luminance ratio for each light source. As shown in FIG. 1 (a), the light source device E is a basic circuit that drives a constant current by connecting a plurality of light sources (LEDs) 1 to 4 in series to a constant current source 5, and specifies a luminance variation adjusting means (not shown in the figure). Z). The brightness variation adjusting means will be sequentially described with reference to other drawings.

  Each of the plurality of LEDs 1 to 4 is connected in parallel with a control element FET including a transistor (hereinafter also referred to as “FET (especially a field effect transistor)”) 1 to 4. If attention is paid to only ~ 4, they are connected in series. Each of these FETs 1 to 4 is PWM-controlled by the PWM signals for the light sources 1 to 4 and individually turned on to individually bypass the applied voltage (forward voltage drop) of each of the LEDs 1 to 4 and turn off the bypassed LEDs. The circuit is configured so that the OFF period to be set can be set. Note that a high-power LED has high brightness and good power efficiency, and is suitable for reduction in size and weight.

Hereinafter, the operation of the light source device E will be described.
From a plurality of LEDs 1 to 4 connected in series to a constant current source 5 lit at a constant current, a reference current obtained by continuously lighting a reference light source 1 that is observed to have the lowest luminance due to luminance variation and emitting light at a maximum luminance is connected in series. It supplies to the both ends of several LED1-4 connected. The PWM control circuit 6 individually outputs the PWM signals for the light sources 1 to 4 based on the luminance suppression data for each light source.

  The PWM control circuit 6 constituting a part of the brightness variation adjusting means is for each light source capable of individually controlling the ON / OFF of the FET1 to FET4 based on the brightness suppression data for each light source shown in FIG. Outputs the PWM signal. Each light source PWM signal is input to each gate of FET1 to FET4, and controls the OFF period of FET1 to FET4.

  The constant current source 5 connects a plurality of LEDs 1 to LED4 and a current detection resistor r in series, and supplies a constant current as a constant current source for these. The current detection resistor r has a very small resistance value, and is detected as a current value I passing through the resistor r = voltage V / resistance r (also used as a sign), and is always constant by feeding back a feedback signal to the constant current source 5. Is stably supplied, and the plurality of LEDs 1 to 4 are turned on.

  Therefore, the PWM signals for the light sources 1 to 4 to be controlled based on the luminance suppression data for each light source are individually output from the PWM control circuit 6. When the PWM control circuit controls the OFF period of each of the light sources 1 to 4 by the bypass ON of each of the control elements FET1 to FET4 based on the luminance suppression data for each light source, the luminance is increased by a short amount of the OFF period, It has the effect of lowering the brightness for a long time.

  With this action, constant current control is performed so that the maximum luminance of the darkest LED is continuously emitted as the reference light source 1. Then, by limiting and suppressing the LEDs 2 to 4 other than the reference light source 1 that are too bright beyond the reference light source, it is possible to individually adjust the luminance variation. Since there is no power consumption during the OFF period in which the luminance is suppressed, power efficiency is good.

  In this way, the plurality of LEDs 1 to 4 including the luminance variation with respect to the current value are connected in series to control the OFF period based on the constant current driving and the luminance suppression data for each light source, thereby improving the power efficiency and reducing the luminance variation. Individual adjustments are possible.

  Note that the luminance suppression data for each light source is input to the PWM control circuit 6 so as to exclusively control the OFF periods of the plurality of LEDs 1 to 4 connected in series. The brightness suppression data for each light source is created, for example, by a person during a general operation test at the stage of producing and shipping inspection of the light source device E, and is stored in a memory (not shown) so as to be readable.

  Specifically, the luminance of the plurality of LEDs 1 to 4 including the luminance variation with respect to the current value is observed in the operating state of the light source device E. If the LED 1 is dark, it is used as a reference light source, and each of the other LEDs 2 to 4 The brighter the brightness, the more appropriate it is. It is also possible to automatically perform real-time observation along FIG.

  The OFF periods of the LEDs 1 to 4 are ON periods of the control elements FET1 to FET4 that bypass the LEDs 1 to 4, respectively. A plurality of LEDs 1 to 4 are connected in series to the current source 5, and control elements FET 1 to FET 4 connected in parallel for each of the light sources 1 to 4 are also connected in series to the current source 5.

  Here, if the OFF periods of the LEDs 1 to 4 are not exclusive, there is a risk that the control elements FET1 to FET4 are all turned on simultaneously without resistance and the current source 5 is short-circuited. Can avoid the dangers. Further, among the plurality of LEDs 1 to 4, only a single LED is turned off, not a large number, and power fluctuations can be reduced and stabilized.

  Note that the circuit shown in FIG. 1A shows only a single color configuration for the sake of simplicity, but in actuality, red, green, and blue (hereinafter, each color is referred to as “R”, “G”, “B”). For each color, the same circuit is configured to form three primary color LEDs.

The luminance suppression data for each light source is set as follows.
(1) The darkest LED 1 has a maximum luminance of 100% as the reference light source 1, and is driven with a constant current so that it is continuously lit without being driven with a pulse. Thus, it is defined that the luminance suppression data for each light source for continuous lighting = 0.
(2) Except for the reference light source 1, it is too bright. Therefore, the luminance variation is individually adjusted by suppressing the luminance. The correction multiple (reciprocal of the luminance ratio) for aligning the brightness of the reference light source 1 to 100% is displayed in%, and 100−correction multiple = brightness suppression data is illustrated in FIG. .

  The PWM control circuit 6 exclusively inserts an OFF period for the LEDs 2 to 4 based on the luminance suppression data shown in FIG. Here, the timing that can be turned off for each of the light sources 1 to 4 is determined in an exclusive and uniform manner. For example, these are exclusive timings of LED2 OFF timing, LED3 OFF timing, and LED4 OFF timing.

  FIG. 2 is an operation explanatory diagram when the OFF timing for each of the light sources 2 to 4 is simply divided into three in the light source device E according to the present embodiment. (A) Timing chart, (b) Luminance for each of the LEDs 1 to 4 It is the ratio (%) of the suppression data and the OFF period. As shown in FIG. 2A, brightness control is performed by varying the ON timing in each OFF timing.

  In addition, LED1-LED4 is LED of the same color over the whole figure which showed the timing chart. That is, it is a description regarding the luminance variation adjusting means for adjusting the luminance variation between LEDs of all red (R), all green (G), or all blue (B). Since the denominator becomes 1/3 by dividing into three, as shown in FIG. 2B, the ratio of the OFF period for each light source is three times that of the luminance suppression data.

  FIG. 3 is an explanatory diagram of an operation in which one cycle is divided into 300 equally and an OFF timing is assigned in the light source device according to the present embodiment. (A) Timing chart, (b) Luminance suppression data for each light source and OFF insertion Is the number of times. As shown in FIG. 3A, one cycle is divided into 300 equal parts, and the OFF timing is assigned in the order of LED2, LED3, and LED4.

As shown in FIG. 3B, since the OFF period is determined from the luminance suppression data value, it is desirable to allocate the OFF timing as evenly as possible. Specifically, it is as follows.
LED2 has a luminance suppression data value of 17. Insert OFF only 51 (= 17 × 3) times.
LED3 has a luminance suppression data value of 5. Insert OFF only 15 (= 5 × 3) times.
LED4 has a luminance suppression data value of 9. Insert OFF only 27 (= 9 × 3) times.
The relationship between the number of OFF insertions and the insertion position (timing) may be stored in advance as a table in a storage unit (not shown) of the PWM control circuit 6 or may be calculated each time by an arithmetic program.

  The OFF timing time assigned to each of the light sources 1 to 4 shown in FIGS. 2 and 3 is a uniform timetable (same width) for convenience of explanation, but the luminance variation of each of the light sources 1 to 4 is large. Therefore, it is preferable to divide by the luminance suppression data ratio. In this way, the constant current control is performed so that the maximum luminance of the darkest LED 1 is the reference light source 1 so as to emit light continuously. The LEDs 1 to 4 including the reference light source 1 include luminance variations with respect to the current value, but the luminance variations generated by connecting the plurality of LEDs 1 to 4 in series and driving at constant current can be individually adjusted.

  Here, an example in which the OFF timing is unevenly distributed will be described with reference to FIGS. 4 and 5. Since the luminance suppression data ratio is 17: 5: 9, the time distribution of the OFF timing of each color in one cycle is 17 / (17 + 5 + 9) = 17/31 = 55%, 5/31 = 16%, 9 respectively. The prescribed ratio is / 31 = 29%.

  FIG. 4 is a timing chart of control in which each of the light sources 1 to 4 is divided at a specified ratio in one cycle and an OFF timing is assigned by dividing one cycle into 300 equal parts in the light source device according to the present embodiment. As shown in FIG. 4, it divides | segments by the said prescription | regulation ratio simply, and controls with the resolution which divided | segmented the whole period into 300 equally regarding the OFF timing of each light source 1-4. Here, 51/300 = 17% of one cycle for 51 LEDs2, 15/300 = 5% of one cycle for 15 LEDs3, 27/300 = 9% of one cycle for 27 LEDs4 It is turned off only during this period.

  FIG. 5 shows a light source device according to the present embodiment. One cycle is divided into 100 equal parts, and each divided OFF timing is divided by a prescribed ratio for each of the light sources 1 to 4. It is a timing chart of allocation control. As shown in FIG. 5, one cycle is equally divided into 100, and the divided OFF timing periods are further divided into light sources 1 to 4 at the specified ratio, and OFF timings are sequentially assigned to the light sources 1 to 4.

  FIG. 6 is a timing chart for controlling the width of the light source device E according to the present embodiment by dividing the entire OFF timing into 300 equal parts and rearranging the light sources 1 to 4 according to the specified ratio. In FIG. 3 to FIG. 6, dividing one cycle into 100 equal parts or 300 equal parts is merely an example, and an appropriately set division number may be adopted.

Next, an application embodiment of the light source device E will be described with reference to FIGS.
FIG. 7 is a block diagram showing an example in which the light source device according to the present embodiment is applied to a color sequential drive image display device and a projector using a digital micromirror device (DMD: trademark of Texas Instruments Incorporated). The image display device 7 shown in FIG. 7 has a basic circuit configuration in which the R light source module 8R, the G light source module 8G, and the B light source module 8B are driven at a constant current by a constant current source 5 ′.

  The R light source module 8R uses the R luminance suppression data, and controls the OFF timing of the FET • R by the R light source selection signal. Similarly, the G light source module 8G uses the G luminance suppression data, and controls the OFF timing of the FET • G by the G light source selection signal. Similarly, the B light source module 8 </ b> B uses the B luminance suppression data, and controls the OFF timing of the FET • B by the B light source selection signal. In this way, the entire RGB light source modules 8R, 8G, and 8B are ON / OFF controlled by the RGB light source selection signals.

  Note that the image display device 7 shown in FIG. 7 is suitable when the current values of the RGB light source modules 8R, 8G, and 8B are not significantly different. Otherwise, it is possible to adapt to practical use by changing the time distribution of each RGB color and aligning the current values.

  FIG. 8 is a block diagram showing an application example of the light source module 8 by the light source device according to the present embodiment. The configuration and operation of the light source module 8 shown in FIG. 8 are substantially the same as those of the light source device E described with reference to FIG. In the case of DMD, the color reproducibility can be improved by setting one period below 1 / natural number of the minimum response time of the display device.

  FIG. 9 is an explanatory diagram corresponding to the number of light sources of the light source device E according to the present embodiment, (a) a circuit diagram using four LEDs, and (b) a comparison diagram of exclusive correction ranges (%) according to the number of light sources. . As shown to Fig.9 (a), a high-intensity output is efficiently obtained by using four high output square type | mold LEDs for LED1-4. Therefore, it is suitable for a projector that requires a high luminance output.

  As shown in FIG. 9B, the exclusive correction range for each number of light sources decreases as the number of light sources increases, and is 33% when the number of light sources is 4, and 11% when the number of light sources is 10. This is because the exclusive control is performed in the light source device E, so that the luminance adjustment range gradually decreases as the number of light sources increases. However, since the luminance variation of LEDs 1 to LEDn is not so large, even if four or more are used, it is within the controllable range, and is sufficiently suitable for practical use as a projector.

Here, an example at the time of equal division will be described with reference to FIGS.
FIG. 10 is a timing chart of the operation of turning off two of the light source devices E according to the present embodiment when they are out of the exclusive correction range for each number of light sources and shifted by half.
FIG. 11 is a timing chart of control in the light source device E according to the present embodiment, in which one cycle is equally divided into 100 in the case shown in FIG.

  As shown in FIGS. 10 and 11, when the luminance variation is outside the exclusive correction range, up to two LEDs that are simultaneously turned off are allowed, but the reason for avoiding the simultaneous OFF timing as much as possible is as follows. This is to alleviate fluctuations in power consumption, and if the control is shifted by half, it is less likely to impair improvement and stabilization of power efficiency. Note that the same method can be used during non-uniform division.

  FIG. 12 is a schematic circuit diagram showing a light source device E ′ that enables real-time correction by feedback from the luminance sensor 9 in the light source device E shown in FIG. 1 according to the present embodiment. The light source device E ′ shown in FIG. 12 has a luminance sensor 9 disposed in the vicinity of the LEDs 1 to 4 of the light source device E as a base shown in FIG. 1 and real-time correction by feedback from the luminance sensor 9. The brightness sensor control circuit 12 is made available.

  The luminance sensor control circuit 12 generates light source-specific luminance suppression data based on the luminance data from the luminance sensor 9 and inputs it to the PWM control circuit 6 ′. Since the luminance sensor 9 detects the luminance data of each of the LEDs 1 to 4 in real time, it is possible to save the trouble of creating the luminance suppression data for each light source, for example, in an operation test (inspection before factory shipment) immediately before shipping the product from the factory. In addition, the light source device E ′ corrects luminance variations due to changes over time in addition to the temperature characteristics of the LEDs 1 to 4 in real time, so that it is possible to always provide a uniform light source without luminance variations.

  FIG. 13 is a flowchart showing a light source control method according to the present invention. Next, a light source control method according to the present invention will be described with reference to FIG. As shown in FIG. 13, first, in the darkest light source specifying step (S1), the brightness variation of each of the plurality of light sources (LEDs) 1 to 4 is observed, and the reference light source 1 having the lowest brightness is specified from the LEDs 1 to 4. . This darkest light source specifying step (S1) is automatically handled by the light source device E ′ shown in FIG. 12, but if not, it may be executed manually by an inspector or the like in addition to pre-shipment inspection. Absent.

  Next, in the reference current supply step (S2), a constant current that emits light with the maximum brightness by continuously lighting the reference light source 1 is determined as the reference current and supplied from the constant current source 5, and the light source devices E and E 'are operating. Keeps the reference current flowing.

  Then, in the luminance suppression data generation step for each light source (S3), data relating to the luminance variation for each of the LEDs 1 to 4 is generated as luminance suppression data for each light source. Next, in each light source OFF period control step (S4), the PWM control signal for each light source 1 to 4 is input to the gates of the control elements FET1 to FET4 based on the luminance suppression data for each light source to bypass each light source 1 to 4. By turning on, the OFF period of each LED1-4 is controlled.

  In addition, according to the light source device E shown in FIG. 1, the light source device E ′ shown in FIG. 12, the light source module 8 shown in FIG. 8, and the light source device E for projector shown in FIG. Even when a failure occurs, it is possible to return from a state in which all LEDs are extinguished by always bypassing the failure location.

  As described above, according to the light source devices E and E ′ including the luminance variation adjusting means, the luminance variations of the LEDs 1 to 4 that are connected in series to the constant current sources 5 and 5 ′ are individually adjusted. Providing a uniform light source and improving the power utilization efficiency, it is possible to cope with power saving.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the present embodiment, the LEDs 1 to 4 are used as light sources, but these may be replaced with similar solid light source elements.

It is explanatory drawing of the light source device which concerns on this embodiment, (a) Schematic circuit diagram, (b) Correction magnification with respect to luminance ratio according to light source, and luminance suppression data. In the light source device according to the present embodiment, it is an operation explanatory diagram when the OFF timing for each light source is simply divided into three, (a) timing chart, (b) luminance suppression data for each light source and the ratio of the OFF period ( %). In the light source device according to the present embodiment, it is an explanatory diagram of an operation in which one cycle is divided into 300 equal parts and OFF timing is assigned, (a) a timing chart, (b) luminance suppression data for each light source, and the number of OFF insertions. . In the light source device according to the present embodiment, it is a timing chart of control in which each light source is divided at a specified ratio in one cycle, and an OFF timing is assigned by dividing one cycle into 300 equal parts. In the light source device according to the present embodiment, one cycle is divided into 100 equal parts, each divided OFF timing is divided by a specified ratio for each light source, and OFF timing is sequentially assigned to each light source. In the light source device according to the present embodiment, the entire OFF timing is divided into 300 equal parts, and the width is rearranged according to the prescribed ratio for each light source. It is a block diagram which shows the example which applied the light source device which concerns on this embodiment to the image display apparatus of color sequential drive by DMD etc. FIG. It is a block diagram which shows the application example of the light source module by the light source device which concerns on this embodiment. It is explanatory drawing corresponding to the light source device according to this embodiment according to the number of light sources, (a) a circuit diagram using four LEDs, (b) a comparison diagram of the exclusive correction range (%) by the number of light sources. In the light source device according to the present embodiment, when it is outside the exclusive correction range by the number of light sources, it is a timing chart of the operation of turning off two simultaneously by shifting by half. FIG. 11 is a control timing chart in which one cycle is equally divided into 100 and an OFF timing is assigned in the light source device according to the present embodiment shown in FIG. 10. FIG. 2 is a schematic circuit diagram showing a light source device capable of real-time correction by feedback from a luminance sensor in the light source device shown in FIG. 1 according to the present embodiment. 3 is a flowchart illustrating a light source control method according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1-4 ... Light source, 1 ... Reference | standard light source (same code | symbol), 5 ... Constant current source, 6, 6 '... PWM control circuit, 7 ... Image display apparatus, 8, 8R, 8G, 8B ... Light source module, 9 ... Luminance Sensor, 12 ... Luminance sensor control circuit, E, E '... Light source device, FET1-FET4 ... Control element, S1 ... Darkest light source identification step, S2 ... Reference current supply step, S3 ... Luminance suppression data generation step for each light source, S4 ... Each light source OFF period control step

Claims (7)

A plurality of light sources connected in series;
A constant current source that supplies a reference current that emits light at a maximum brightness by continuously turning on a reference light source that has been observed to have the lowest brightness due to brightness variation among the constant current lighting of the light source; and
A control element that is connected in parallel to each of the plurality of light sources and bypasses the applied voltage of each of the light sources by PWM control;
A light source comprising: a PWM control circuit for individually outputting a PWM signal for each light source for controlling an OFF period of each light source based on bypass suppression of each control element based on luminance suppression data for each light source; apparatus.   The light source device according to claim 1, wherein an LED is used as the light source.   The luminance control data for each light source is configured so as to exclusively control an OFF period of each of the plurality of light sources connected in series by being input to the PWM control circuit. Item 3. A light source device according to item 1 or 2. A luminance sensor that detects luminance data for each light source disposed in the vicinity of each of the plurality of light sources in real time;
4. A luminance sensor control circuit that generates luminance suppression data for each light source based on the luminance data from the luminance sensor and inputs the luminance suppression data to a PWM control circuit. 5. The light source device according to item.   An image display device comprising the light source device according to any one of claims 1 to 4.   A projector comprising the image display device according to claim 5. A darkest light source specifying step of observing a luminance variation of each of a plurality of light sources and specifying a reference light source having the lowest luminance among the light sources;
A reference current supply step of setting a constant current that emits light at a maximum brightness by continuously lighting the reference light source as a reference current and supplying from the constant current source;
A light source-specific luminance suppression data generation step for generating data regarding luminance variation for each light source as luminance suppression data for each light source;
Each light source OFF period control step for controlling the OFF period of each light source by inputting the PWM control signal for each light source to the gate of each control element based on the luminance suppression data for each light source and bypassing each light source, A light source control method comprising:

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